Controlling wind noise in a bilateral microphone array

Abstract

A pair of earphones have microphone arrays each providing a plurality of microphone signals. A processor receives the microphone signals and applies a first set of filters to a subset of the plurality of microphone signals from each of the arrays, the first set of filters inverting the signals below a cutoff frequency, and provides the first-filtered signals and the remainder of the microphone signals from each of the arrays to a second set of filters. The processor uses the second set of filters to combine the signals to generate a far-field signal that is more sensitive to sounds originating a short distance away from the earphones than to sounds close to the earphones above the cutoff frequency, and omnidirectional below the cutoff frequency, determines a level of wind noise present in the microphone signals, and adjusts the cutoff frequency as a function of the determined level of wind noise.

What is claimed is: 
     
       1. An apparatus comprising:
 a first earphone having a first microphone array providing a first plurality of microphone signals, and a first speaker; 
 a second earphone having a second microphone array providing a second plurality of microphone signals, and a second speaker; and 
 a processor receiving the first plurality of microphone signals and second plurality of microphone signals, and configured to:
 apply a first set of filters to a subset of the plurality of microphone signals from each of the first microphone array and the second microphone array, the first set of filters inverting the signals below a cutoff frequency; 
 provide the first-filtered signals and the remainder of the microphone signals from each of the first microphone array and the second microphone array to a second set of filters; 
 use the second set of filters to combine the microphone signals to generate a far-field signal that is more sensitive to sounds originating a short distance away from the apparatus than to sounds close to the apparatus above the cutoff frequency, and omnidirectional below the cutoff frequency; 
 determine a level of wind noise present in the microphone signals; 
 adjust the cutoff frequency as a function of the determined level of wind noise; and 
 provide the far-field signal to the speakers for output. 
 
 
     
     
       2. The apparatus of  claim 1 , wherein the processor is further configured to:
 after generating the far-field signal in the second set of filters, apply gain to the output of the filters below a second cutoff frequency which is a function of the first cutoff frequency. 
 
     
     
       3. The apparatus of  claim 1 , wherein the processor is further configured to:
 after generating the far-field signal in the first set of filters, apply a high-pass filter to the output of the filters. 
 
     
     
       4. The apparatus of  claim 1 , wherein the processor is further configured to:
 determine a total low-frequency energy present in the microphone signals; and 
 upon determining that the total sound level is below a first threshold, and the level of wind noise is below a second threshold, increase the cutoff frequency of the first set of filters. 
 
     
     
       5. The apparatus of  claim 1 , wherein generating the far-field signal comprises, in the processor:
 determining a total low-frequency energy present in the microphone signals; 
 computing a sum of the microphone signals; 
 computing a difference of the microphone signals; 
 comparing the sum of the microphone signals to the difference of the microphone signals and to the total low-frequency energy; and 
 determining the cutoff frequency based on the results of the comparison. 
 
     
     
       6. The apparatus of  claim 5 , wherein computing the difference of the microphone signals comprises:
 computing a first difference of microphone signals in the first plurality of microphone signals, 
 computing a second difference of microphone signals in the second plurality of microphone signals, and 
 computing a difference of the first difference and the second difference as the difference of the microphone signals. 
 
     
     
       7. An apparatus comprising:
 a first earphone having a first microphone array providing a first plurality of microphone signals, and a first speaker; 
 a second earphone having a second microphone array providing a second plurality of microphone signals, and a second speaker; and 
 a processor receiving the first plurality of microphone signals and second plurality of microphone signals, and configured to:
 use a first set of filters to combine the microphone signals to generate a far-field signal that is more sensitive to sounds originating a short distance away from the apparatus than to sounds close to the apparatus above a cutoff frequency, and omnidirectional below the cutoff frequency; 
 determine a level of wind noise present in the microphone signals; 
 adjust the cutoff frequency as a function of the determined level of wind noise; 
 provide the far-field signal to the speakers for output; 
 use a second set of filters to combine the microphone signals to generate a near-field signal that is more sensitive to voice signals from a person wearing the earphones than to sounds originating away from the apparatus; 
 combine the microphone signals to generate an omnidirectional signal; 
 combine the near-field signal and the omnidirectional signal using a weighted sum, the weight being a function of the determined level of wind noise to generate a communication signal; and 
 provide the communication signal to a communication system. 
 
 
     
     
       8. The apparatus of  claim 7 , wherein the processor is configured to:
 determine the level of wind noise for adjusting the cutoff frequency based on a comparison of a sum of the microphone signals to a difference of the microphone signals; and 
 determine the level of wind noise for adjusting the weight applied to the near field signal in the communication signal based on a comparison of the near field signal to the omnidirectional signal. 
 
     
     
       9. The apparatus of  claim 7 , wherein generating the far-field signal comprises, in the processor:
 applying an all-pass filter to a subset of the plurality of microphone signals from each of the first microphone array and the second microphone array, the all-pass filter inverting the signals below the cutoff frequency; and 
 providing the all-pass-filtered signals and the remainder of the microphone signals from each of the first microphone array and the second microphone array to the first set of filters. 
 
     
     
       10. The apparatus of  claim 7 , wherein generating the near-field signal and omnidirectional signal comprises, in the processor:
 applying a third set of filters to a first subset of the plurality of microphone signals from each of the first microphone array and the second microphone array; 
 applying a fourth set of filters to a second subset of the plurality of microphone signals from each of the first microphone array and the second microphone array; 
 combining the filtered first subset with the filtered second subset to generate the near-field signal; and 
 summing the first subset and the second subset to generate the omnidirectional signal. 
 
     
     
       11. The apparatus of  claim 10 , wherein generating the near-field signal and omnidirectional signal further comprises:
 summing the first subset and providing the summed first subset to the third set of filters; 
 summing the second subset and providing the summed second subset to the fourth set of filters; 
 summing the summed first subset and the second summed subset to generate the omnidirectional signal. 
 
     
     
       12. The apparatus of  claim 10 , wherein the processor comprises a plurality of sub-processors, and the summing of the first and second subsets is performed by a separate sub-processor from the applying of the third and fourth filters and combining of the filtered subsets. 
     
     
       13. A method comprising, in a processor:
 receiving, from a first earphone having a first microphone array, a first plurality of microphone signals; 
 receiving, from a second earphone having a second microphone array, a second plurality of microphone signals; and 
 applying a first set of filters to a subset of the plurality of microphone signals from each of the first microphone array and the second microphone array, the first set of filters inverting the signals below a cutoff frequency; 
 providing the first-filtered signals and the remainder of the microphone signals from each of the first microphone array and the second microphone array to a second set of filters; 
 using the second set of filters to combine the microphone signals to generate a far-field signal that is more sensitive to sounds originating a short distance away from the earphones than to sounds close to the apparatus above the cutoff frequency, and omnidirectional below the cutoff frequency; 
 determining a level of wind noise present in the microphone signals; 
 adjusting the cutoff frequency as a function of the determined level of wind noise; and 
 providing the far-field signal to first and second speakers in the respective first and second earphones for output. 
 
     
     
       14. The method of  claim 13 , further comprising, in the processor:
 after generating the far-field signal in the second set of filters, applying gain to the output of the filters below a second cutoff frequency. 
 
     
     
       15. The method of  claim 13 , further comprising, in the processor:
 after generating the far-field signal in the first set of filters, applying a high-pass filter to the output of the filters. 
 
     
     
       16. The method of  claim 13 , further comprising, in the processor:
 determining a total sound level present in the microphone signals; and 
 upon determining that the total sound level is below a first threshold, and the level of wind noise is below a second threshold, increasing the cutoff frequency of the first set of filters. 
 
     
     
       17. A method comprising, in a processor:
 receiving, from a first earphone having a first microphone array, a first plurality of microphone signals; 
 receiving, from a second earphone having a second microphone array, a second plurality of microphone signals; 
 using a first set of filters to combine the microphone signals to generate a far-field signal that is more sensitive to sounds originating a short distance away from the apparatus than to sounds close to the apparatus above a cutoff frequency, and omnidirectional below the cutoff frequency; 
 determining a level of wind noise present in the microphone signals; 
 adjusting the cutoff frequency as a function of the determined level of wind noise; 
 providing the far-field signal to first and second speakers in the respective first and second earphones for output; 
 using a second set of filters to combine the microphone signals to generate a near-field signal that is more sensitive to voice signals from a person wearing the earphones than to sounds originating away from the earphones; 
 combining the microphone signals to generate an omnidirectional signal; 
 combining the near-field signal and the omnidirectional signal using a weighted sum, the weight being a function of the determined level of wind noise to generate a communication signal; and 
 providing the communication signal to a communication system. 
 
     
     
       18. The method of  claim 17 , further comprising, in the processor:
 determining the level of wind noise for adjusting the cutoff frequency based on a comparison of a sum of the microphone signals to a difference of the microphone signals; and 
 determining the level of wind noise for adjusting the weight applied to the near field signal in the communication signal based on a comparison of the near field signal to the omnidirectional signal. 
 
     
     
       19. The method of  claim 17 , wherein generating the far-field signal comprises, in the processor:
 applying an all-pass filter to a subset of the plurality of microphone signals from each of the first microphone array and the second microphone array, the all-pass filter inverting the signals below the cutoff frequency; and 
 providing the all-pass-filtered signals and the remainder of the microphone signals from each of the first microphone array and the second microphone array to the first set of filters. 
 
     
     
       20. The method of  claim 17 , wherein generating the near-field signal and omnidirectional signal comprises:
 applying a third set of filters to a first subset of the plurality of microphone signals from each of the first microphone array and the second microphone array; 
 applying a fourth set of filters to a second subset of the plurality of microphone signals from each of the first microphone array and the second microphone array; 
 combining the filtered first subset with the filtered second subset to generate the near-field signal; 
 summing the first subset and the second subset to generate the omnidirectional signal. 
 
     
     
       21. The method of  claim 20 , wherein generating the near-field signal and omnidirectional signal further comprises:
 summing the first subset and providing the summed first subset to the third set of filters; 
 summing the second subset and providing the summed second subset to the fourth set of filters; 
 summing the summed first subset and the second summed subset to generate the omnidirectional signal. 
 
     
     
       22. The method of  claim 20 , wherein the processor comprises a plurality of sub-processors, and the summing of the first and second subsets is performed by a separate sub-processor from the applying of the third and fourth filters and combining of the filtered subsets.